Chemical equilibrium and E value of Zn (ZnE) in inceptisols and entisols of tropical india

Summary The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol and inceptisols. The rate of isotopic exchange between⁶⁵Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days. In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days. This indicated that the chemistry and availability of Zn in soil would depend on soil types. When Zn_E was estimated by applying activity after equilibrium with carrier Zn and by applying activity with carrier Zn before equilibrium was set, there was no agreement in Zn_E in two methods. Increasing Zn_E with increasing Zn dose was observed by both methods only in alkaline typic ustochrept (4). In some soils higher E values than added amounts were observed, whereas, in soil 8 negative E values were obtained. The E values become erratic and are over estimated where complex reactions take place due to high pH, high O.C. and high complex forming elements.     

Regulation of Muscarinic Receptor-Mediated Cyclic GMP Synthesis by Cultured Mouse Neuroblastoma Cells

Mouse neuroblastoma clone N1E-115 has muscarinic acetylcholine receptors that mediate cyclic GMP synthesis. This receptor-mediated response is not significantly higher than background until the cells have been maintained in the stationary phase for at least 1 week. The basis of the influence of time in culture on the cyclic GMP response was investigated. The relative amount of cyclic GMP synthesized by intact cells was measured by radioactively labeling the GTP pool with [³H]guanine, incubating cells with agonists, and then chromatographically isolating [³H]cyclic GMP. Carbamylcholine-, ionophore X-537A-, and sodium azide-induced cyclic GMP formation increased with time in culture to a maximum of 13-, 9-, and 2.5-fold above basal, respectively. There was no change in the number or the apparent affinity of the muscarinic receptors as measured by [³H]quinuclidinyl benzylate ([³H]QNB) binding. In addition, there was no change in the apparent affinity of the receptors for agonist as measured by the ability of carbamylcholine to displace the specific binding of [³H]QNB. Guanylate cyclase activity per milligram protein and per cell in-creased six- and sevenfold, respectively, from day 0 to day 22. However, this increase in guanylate cyclase appeared to precede the marked increase in sensitivity of the cells to agonists. These data suggest that, in addition to guanylate cyclase and muscarinic receptors, there is another factor which is responsible for the development of this muscarinic receptor-mediated response.     

Morphine addiction and withdrawal alters brain peptide concentrations

This study demonstrates that, during morphine addiction and withdrawal in rats profound alterations in the concentrations of a variety of brain peptides occur. Somatostatin, cholecystokinin, neurotensin and substance P concentrations increased during morphine addiction. Naloxone-induced withdrawal decreased brain concentrations of TRH, somatostatin, neurotensin and substance P. Naloxone alone decreased thalamic substance P and neurotensin concentrations. Vasoactive intestinal peptide concentrations were unaltered by any of the treatments. The fall in the tissue concentration of somatostatin during naloxone-induced withdrawal correlated well with the fall in the circulating growth hormone, suggesting that this could be secondary to somatostatin release. Our data support the hypothesis that brain peptides, acting locally in the brain as neuromodulators, play an important role in the genesis of the syndromes of morphine addiction and withdrawal.     

Inhibition of the positive inotropic effect of anthopleurin-A (AP-A) by dantrolene

The effect of dantrolene on the positive inotropic effects (PIE) of three cardiotonic agents was assessed on rat and rabbit atria. Dantrolene (10^?5M) had no effect on contractile tension or on the PIE to isoproterenol (10^?10?10^?7M) or ouabain (10^?6?10^?4). The dose-response curve for the PIE of anthopleurin-A (AP-A) was shifted to the right in rat and rabbit atria by dantrolene (10^?4?10^?6M). The maximum effect and the concentration of AP-A required for it remained the same. The results suggest that the PIE of AP-A involves intracellular translocation of calcium, unlike those of isoproterenol and ouabain which require increased transmembrane calcium flux. This conclusion is supported by the observation that the exchange and distribution of the labile calcium involved in excitation-contraction coupling was unaffected by AP-A (10^?8M), by dantrolene (10^?6M) or by the combination. Therefore, AP-A may produce its cardiotonic effect by a action at an intracellular site, a mechanism unlike that of isoproterenol or ouabain.     

Ellipticines and human liver microsomes: Spectral interaction with cytochrome P-450 and hydroxylation. Inhibition of aryl hydrocarbon metabolism and mutagenicity

Some pharmacological properties of ellipticine (E) and its derivatives linked to their interaction with cytochrome P-450 have been investigated with human liver microsomes. 9-Hydroxyellipticine (9-OHE) interacts with human liver cytochrome P-450 exhibiting a type II spectrum (λ_max: 428 nm, K_s = 1.1 μM). After incubation with human liver microsomes the E was converted to 9-OHE; 7-hydroxyellipticine was not produced. The cytotoxic effect of this biotransformation has been evaluated on leukemic L1210 cells, in vitro, and found to be equal to those elicited by liver microsomes of control or phenobarbital (PB) pretreated rats. Moreover, 9-OHE and 9-fluoroellipticine (9-FE) strongly inhibit the benzo[a]pyrene hydroxylase (AHH) activity of human liver microsomes (I₅₀ = 2.6 μM and 1.6 μM, respectively) as well as the mutagenesis induced by the polycyclic aromatic hydrocarbon 2-acetylaminofluorene (AAF); 1 μg/plate of each of these compounds is able to inhibit by more than 50% the mutagenicity of 5 μg/plate AAF.     

Neonatal thyroxine treatment enhances classical conditioning in the infant rat

Neonatal rats injected with either thyroxine (T₄) or vehicle (NaOH) on postnatal Days 1, 2, and 3 were given classical-conditioning pairings of an odor with footshock when 7, 9, or 11 days of age. In accord with the conventional acceleration of other indices of maturation following the T₄ treatment, 24-hr retention of the conditioned odor aversion was substantially enhanced among the 11 day-old rats given the earlier T₄ treatment. This effect was marginally significant among 9-day olds but not among 7-day olds.     

Genetic analysis of transpositions in the lac region of Escherichia coli

The lac region of Escherichia coli, carried on an F′ lacproB episome, was used as a target for the transposition of several transposable elements. Tn9 shows a preferential integration (by a factor of 50) into a region extending from the end of the Z gene through the Y gene. Throughout the remainder of the lacI, Z and Y genes one other short region, located in the middle of the I gene, is favored for integration. Within these favored regions many different integration points are evident. Inspection of the DNA sequence for the I and Y genes, and parts of the Z gene, shows a strong correlation between A + T richness and regions of preferential integration. Tn5 insertions follow a similar pattern, although with less preference; whereas Tn10 insertions (provided by T. J. Foster), also favor the Y gene and the end of Z, but are distributed among fewer integration points. Most of the Tn3 insertions into the episome are accompanied by a nearby or adjacent deletion.     

Hydroxyurea inhibits ODC induction, but not the G1 to S phase transition.

Chinese hamster ovary cells, selected in mitosis and plated into medium containing hydroxyurea, can progress through G₁ and enter S phase although bulk DNA synthesis is prevented. As the cells progress through G₁ in the presence of hydroxyurea, ornithine decarboxylase activity remains low while general protein synthesis appears unaffected. After hydroxyurea is removed, ornithine decarboxylase activity increases, but only after approximately 20% of the DNA has been replicated. These results suggest that ornithine decarboxylase induction is not essential for cellular progression into S phase but is required for the completion of DNA synthesis.